Portable radiation imaging system and a radiation image detection device equipped with an angular signal output means

ABSTRACT

A portable radiation imaging system is provided which is capable of always performing imaging in a state where the tilt of the radiation emitted from a radiation source in relation to the detection surface of an image detection device is substantially perpendicular. The system is equipped with a tilt adjustment means that makes the tilt of the radiation in relation to the detection surface of a radiation image detection device substantially perpendicular by changing the tilt angle of a radiation source based on an angular signal representing the degree of tilt of the radiation in relation to said detection surface output by an angular signal output means, and a command means that generates an exposure command to the radiation source when the tilt of the radiation to be emitted from said radiation source in relation to the detection surface of said radiation image detection device is substantially perpendicular.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a portable radiation imaging system anda radiation image detection device for said imaging system.

2. Description of the Related Art

Apparatuses for forming radiation images, constituting a radiationsource and a radiation image detection device, such as X-ray imagingsystems and CR systems (as disclosed in, for example, JapaneseUnexamined Patent Publication No. 55(1980)-12429 and Japanese UnexaminedPatent Publication No. 56(1981)-11395 by the present applicant, etc.)are widely used in the medical field.

Today, use of the aforementioned systems is not limited to the imagingrooms of hospitals (treatment settings). Said systems are being broughtinto the ICU ward to take a plurality of images in a short time span, orbrought out to patients and other people desiring treatment outside thehospital and imaging performed at these settings. Systems that can becarried and transported in this manner will be referred to hereinafteras portable radiation imaging systems (as disclosed in JapaneseUnexamined Patent Publication No. 3(1991)-295540.

Meanwhile, to obtain a radiation image appropriate for use in diagnosis,it is necessary to maintain the relative angle between a cassette or thelike which houses an image recording medium such as X-ray film or animaging plate and the radiation source (tubular bulb) substantiallyperpendicular. More specifically, it is said that it is necessary tomaintain the angle between the radiation emitted from the radiationsource and the detection surface of the image detection device such asthe aforementioned cassette or the like substantially perpendicular.This is in order to prevent the occurrence of false images in the casethat, for example, a scattered ray removal grid board is utilized, andalso for reasons of image reproducibility.

However, in the case that a portable radiation imaging system isutilized in, for example, an ICU ward to take many images within a shortperiod of time, it is not possible to maintain the angle between thecassette and the radiation source perpendicular. As the angle changesfor each image, diagnosis utilizing the obtained images becomesdifficult. The same problem arises in the case that the system isbrought outside the hospital to perform imaging in an alternate setting.

SUMMARY OF THE INVENTION

The present invention has been made in view of the above-describedcircumstances, and it is a primary object of the invention to provide aportable radiation imaging system that is capable of performing imagingin a state in which the angle between the radiation emitted from theradiation source and the detection surface of the image detection deviceis substantially perpendicular at all times.

It is another object of the present invention to provide a radiationimage detection device to be utilized by the radiation imaging system ofthe present invention.

The first radiation imaging system according to the present system is aportable radiation imaging system constituting a radiation source and atwo-dimensional radiation image detection device that records aradiation image by detecting the radiation that has been transmittedthrough a subject. The system is characterized by being further equippedwith an angular signal output means that outputs an angular signal whichrepresents the tilt angle between the radiation emitted from theradiation source and the detection surface of the image detectiondevice, and an tilt adjustment means that changes the tilt angle of theradiation source based on the angular signal output from said angularsignal output means so that the angle between the radiation emitted fromthe radiation source and the detection surface of the image detectiondevice becomes substantially perpendicular.

In other words, the first radiation imaging system of the presentinvention is of a type that adjusts the angle between the radiationsource and the detection surface of the radiation image detection deviceby changing the angle on the radiation source side.

The second radiation imaging system according to the present inventionis a portable radiation imaging system constituting a radiation sourceand a two-dimensional radiation image detection device that records aradiation image by detecting the radiation that has been transmittedthrough a subject. The system is characterized by being further equippedwith an angular signal output means that outputs an angular signal whichrepresents the tilt angle between the radiation emitted from theradiation source and the detection surface of the image detectiondevice, and an tilt adjustment means that changes the tilt angle of theradiation image detection device based on the angular signal output fromsaid angular signal output means so that the angle between the radiationemitted from the radiation source and the detection surface of the imagedetection device becomes substantially perpendicular.

In other words, the second radiation imaging system of the presentinvention is of a type that adjusts the angle between the radiationsource and the detection surface of the radiation image detection deviceby changing the angle on the radiation image detection device side.

The third radiation imaging system according to the present invention isa portable radiation imaging system constituting a radiation source anda two-dimensional radiation image detection device that records aradiation image by detecting the radiation that has been transmittedthrough a subject. The system is characterized by being further equippedwith a command means for generating an exposure command to the radiationsource when the angle between the radiation emitted therefrom and thedetection surface of the radiation image detection device issubstantially perpendicular.

In other words, the third radiation imaging system of the presentinvention is of a type that automatically generates an exposure commandat a point when the angle between the radiation to be emitted from theradiation source and the detection surface of the radiation imagedetecting device is made to be substantially perpendicular by adjustingthe tilt on either the radiation source side or the radiation imagedetection device side.

Further, this third system can be combined with the first or secondsystems. That is, it can be of a structure equipped with a tiltadjustment means for changing either the tilt angle on the radiationsource side or the radiation image detection device side. Note that thechanging of the tilt on the radiation source side or the radiation imagedetection device side may be a manual operation.

With regard to the first through third radiation systems describedabove, it is preferable that they be further equipped with a portableshift means for moving either the radiation source or the radiationimage detection device horizontally.

To enable horizontal movement of either the radiation source or theradiation image detection device means that both or one of theseelements becomes capable of motion relative to the other. The object ofsuch structure is to make positional adjustments possible so that theafter either the radiation source or the radiation image detectiondevice is tilted, the central axis of the radiation emitted from theradiation source can be adjusted to be positioned to the substantiallycentral portion of the detecting surface of the radiation imagedetection device or to the vicinity of a target area of a subject. Tothis end, it does not matter if the distance between the radiationsource and the radiation image detection device (the distance along thecentral axis of the radiation) changes. For example, it is possible tomove the radiation source laterally (the axial distance changes). or tomove the radiation source in a parallel direction in relation to thedetection surface of the radiation image detection device (the axialdistance does not change).

The first radiation image detecting device according to the presentinvention is a two-dimensional radiation image detecting device capableof recording a radiation image. Said device is characterized by beingequipped with an angular signal output means that outputs an angularsignal which represents the tilt angle between the radiation emittedfrom the radiation source and the detection surface of the imagedetection device, and is especially suited for use with the first orsecond radiation imaging system described above.

The second radiation image detection device according to the presentinvention is a two-dimensional radiation image detecting device capableof recording a radiation image. Said device is characterized by beingequipped with a command means for generating an exposure command to theradiation source when the angle between the radiation emitted therefromand the detection surface of the radiation image detection device issubstantially perpendicular, and is especially suited for use with thethird radiation imaging system described above.

With regard to the above, a two-dimensional radiation image detectiondevice refers to a device capable of recording a radiation image in atwo-dimensional form.

With regard to this detection device, X-ray film, stimulable phosphorsheets (imaging plate) or the like, for example may be utilized as theimage recording medium. Or, a solid state radiation detection deviceutilizing semiconductors (static electricity recording medium) asdisclosed in Japanese Unexamined Patent Publication Nos. 9(1997)-206293and 9(1997)-321267 or Japanese Unexamined Patent Publication No.2000-105297, for example, may be utilized as the image recording medium.Also, the image recording medium may be housed in a cassette andutilized. Further, the radiation image detection device may be providedwith a grid board to remove the scattered rays generated by the subject.

With regard to the above, the tilt angle between the radiation emittedfrom the radiation source and the detection surface of the radiationimage detecting device refers to the angle formed by the central axis ofsaid radiation and the line normal to the detection surface of saidradiation image detecting device, that is, the incidence angle of thecentral axis of the radiation in relation to said detection surface.

As the angular signal output means that outputs an angular signalrepresenting this tilt angle, any means that can detect said tilt anglemay be utilized. For example, an instrument that measures levelness suchas an electronic level, or an instrument that measures angle such as aprojection style angle sensor may be utilized.

Although it is stated that the tilt of the radiation in relation to thedetection surface of the radiation image detection device is made to besubstantially perpendicular, it is not necessary that said tilt bestrictly perpendicular. It is sufficient to make the tilt approximatelyperpendicular to a grid board or an image recording medium, etc., thatis to maintain a perpendicular relationship therewith according to thesystem structure.

The first or second radiation imaging apparatuses of the presentinvention, in combination with the first radiation image detectiondevice, are structured to change the tilt of the radiation source or theimage detection device according to the degree of tilt therebetween andadjusting said tilt to become substantially perpendicular. Accordingly,imaging is always performed in a state where the angle of the radiationin relation to the detection surface is substantially perpendicular, andan image suitable for use in diagnosis can be obtained.

The third radiation imaging apparatus of the present invention, incombination with the second radiation image detection device, arestructured to generate an exposure command at a point when the centralaxis of the radiation is substantially perpendicular to the detectionsurface. Accordingly, imaging is always performed in a state where theangle of the central axis of the radiation in relation to the detectionsurface is substantially perpendicular, and an image suitable for use indiagnosis can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view that shows the structure of the firstembodiment of the radiation imaging system of the present invention.

FIG. 2A and FIG. 2B are schematic views that show the radiation imagedetection device.

FIG. 3 is a schematic view that shows the structure of the secondembodiment of the radiation imaging system of the present invention.

FIG. 4 shows an example of a tilt adjusting means.

FIG. 5 shows an example of a shift means.

FIG. 6 is a schematic view that shows one example of a structure for thethird embodiment of the radiation imaging system of the presentinvention.

FIG. 7 is a schematic view that shows an alternate structure for thethird embodiment of the radiation imaging system of the presentinvention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, the embodiments of the present invention will be describedin detail with reference to the drawings.

FIG. 1 is a schematic view that shows the structure of the firstembodiment of the radiation imaging system of the present invention, andFIGS. 2A and 2B are schematic views that show the radiation imagedetection device.

The first embodiment of the radiation imaging system shown in FIG. 1 isa portable system of the type that adjusts the angle between the centralaxis of the radiation and the detection surface of the radiation imagedetection device to become perpendicular by changing the tilt on theradiation source side. It will be described in detail below.

As shown in FIG. 1, the first embodiment of the radiation imaging system1 comprises: a radiation source 10 that emits radiation L1; and a twodimensional radiation image detection device that records a radiationimage by detecting the radiation L2 which has passed through a subject 9after being emitted from said radiation source 10. The radiation source10 and the radiation image detection device 20 are structured to becarriable. Although not shown in the figure, it is preferable to providea sensor that detects the horizontal position of the center of eitherthe detection device 20 or the subject 9.

The system 1 is further equipped with: an angular signal output means 30that outputs an angular signal which represents the tilt angle betweenthe radiation L1 emitted from the radiation source 10 and the detectionsurface of radiation image detection device 20; a tilt adjustment means40 that changes the tilt angle of the radiation source based on theangular signal output from said angular signal output means so that theangle between the radiation emitted from the radiation source and thedetection surface of the image detection device becomes substantiallyperpendicular; and a shift means 50 that enables horizontal movement ofthe radiation source 10. It need not be said that angular signal outputmeans 30, the tilt adjustment means 40, as well as the shift means 50are to be structured so as to be portable.

The subject 9 is placed on a support 91, such as a stretcher or a bed,positioned between the radiation source 10 and the image detectiondevice 20. The image detection device 20 is placed on a holding member70, which is slightly larger than said image detection device 20.

As to the image detection device, one may be utilized which has astimulable phosphor sheet or a solid state radiation detection devicehoused within a cassette having a grid provided on the detection surfaceside facing the radiation source 10 thereof to prevent scattered rays,for example.

With regard to the structure of the first embodiment, the angular signaloutput means 30 is equipped integrally with the radiation imagedetection device 20. Specifically, as shown in FIGS. 2A and 2B, theangular signal output means 30 is provided on a surface (either thedetection surface or the reverse surface) or on a side of the radiationimage detection device. As to the angular signal output means 30, anelectronic level that is capable of outputting an angular signal Srepresenting two dimensional tilt (degree of levelness) utilizing onesensor as show in FIG. 2A maybe used, for example. Or, the angularsignal output means 30 can be composed of an electronic level 30 xcapable of outputting an angular signal Sx representing tilt (tilt inrelation to a horizontal plane) in an x direction and an electroniclevel 30 y capable of outputting an angular signal Sy representing tilt(tilt in relation to a vertical plane) in a y direction as shown in FIG.2B. The two dimensional tilt (degree of levelness) can be recognized bythe two angular signals Sx and Sy.

In either structure, the detected angular signal S or Sx and Sy is inputto the tilt adjustment means 40.

As shown in FIG. 1, as the structure of the shift means 50, one isadopted which is capable of moving the radiation source 10 in the X aswell as the Y directions. As to the structure of the tilt adjustmentmeans 40, one is adopted which is independently rotatable in the X and Ydirections to enable tilting in both the X-Y planes. To this end, itdoes not matter what specific means are utilized. By such a structure,the tilt of the central axis L1 a of radiation L1 emitted from radiationsource 10 in relation to the detection surface of image detection device20 becomes adjustable, and the shift between said central axis L1 a andthe center of the subject 9 or the center of detection device 20 alsobecomes adjustable.

The angular signal detected by the angular signal output means 30 isinput into tilt adjustment means 40. The tilt adjustment means 40changes the tilt angle of the radiation source 10 based on said angularsignal input thereto, thereby making substantially perpendicular thetilt of the radiation L1 in relation to the detection surface of theimage detection device 20. Specifically, the radiation source 10 istilted to correct the horizontal shift of the detection surface of imagedetection device 20.

Note that if the tilt angle of radiation source 10 is changed, therelative position between the central axis L1 a of radiation L1 emittedfrom radiation source 10 and the radiation image detection device 20 orthe subject 9 in the horizontal direction shifts. The amount of thisshift increases as the tilt angle of radiation source 10 increases, andthere are some cases in which a subject image cannot be recorded. Toavoid this, the shift means 50 moves the radiation source 10 in ahorizontal direction so that the central axis L1 a of radiation L1 ispositioned at the approximate center of the detection surface of imagedetection device 20 or in the vicinity of a target area of subject 9.Radiation source 10 as shown by the dotted line in FIG. 1 shows saidradiation source 10 in this state.

By the construction described above, imaging can always be performed ina state where the angle between the central axis L1 a of the radiationand the detection surface is maintained perpendicular, and an imagesuitable for use in diagnosis can be obtained.

Next, the second embodiment of the radiation imaging system of thepresent invention will be described. FIG. 3 is a schematic view thatshows the structure of the second embodiment of the radiation imagingsystem. The radiation imaging system of the second embodiment is aportable system of the type that adjusts the tilt of the central axis L1a of the radiation in relation to the radiation image detection device20 so that it becomes perpendicular by changing the angle on theradiation image detection device 20 side, and with regard to this point,it differs from the first embodiment described above.

For this reason, instead of the tilt adjustment means 40 provided in theaforementioned first embodiment, the radiation imaging system 1 of thesecond embodiment is equipped with a tilt adjustment means 45 thatchanges the tilt angle of radiation image detection device 20 based onangular signal S or Sx and Sy, thereby making said tilt substantiallyperpendicular. The system 1 is further provided with a shift means 55that enables horizontal movement of the radiation image detection device20. The radiation source 10 is oriented so that the emission surfacefaces approximately straight down; that is, so that radiation L1 isemitted approximately straight downward.

As shown in FIG. 3, as the structure of the shift means 55, one isadopted which is capable of moving the image detection device in boththe X and Y directions (the holding member 70 may be movable integrallywith said device). As to the structure of the tilt adjustment means 45,one is adopted which is independently rotatable in the X and Ydirections to enable tilting in both the X-Y planes. To this end, itdoes not matter what specific means are utilized. By such a structure,as in the first embodiment, the tilt of the central axis L1 a ofradiation L1 emitted from radiation source 10 in relation to thedetection surface of image detection device 20 becomes adjustable, andthe shift between said central axis L1 a and the center of the subject 9or the center of detection device 20 also becomes adjustable.

The angular signal detected by the angular signal output means 30 isinput into tilt adjustment means 45. The tilt adjustment means 45changes the tilt angle of the image detection device 20 based on saidangular signal input thereto, thereby making substantially perpendicularthe tilt of the radiation L1 in relation to the detection surface of theimage detection device 20. Specifically, the image detection device istilted to make the detection surface thereof approximately horizontal inrelation to the radiation L1.

Note that with the construction of the second embodiment, even if thetilt angle of image detection device 20 is greatly changed, the amountof shift in the relative position between the central axis L1 a ofradiation L1 emitted from radiation source 10 and the radiation imagedetection device 20 or the subject 9 in the horizontal direction issmall. Therefore it is thought that said horizontal shift virtually hasno influence on image recording. However, in the case that this shiftbecomes a problem, the image detection device should be moved in thehorizontal direction by the shift means 55.

FIG. 4 shows an example of a tilt adjustment means 45. As shown in thefigure, an image detection device 20 composed of an image recordingmedium such as a stimulable phosphor sheet housed in a cassette ispositioned on a holding member 70. The tilt adjustment means 45 iscomposed of tilt adjustment mechanisms (A1˜A4 in the figure) that adjustthe tilt of the image detection device 20 integrally with the holdingmember 70 by changing the amount of space between the holding membermain body 71 and bottom plate 72 that compose said holding member 70.The tilt adjustment means 45 is housed in a case (for example, acassette holder case) not shown in the figure, along with the imagedetection device 20, holding member main body 71, and the bottom plate72, and provided underneath the subject 9. Note that the bottom plate 72may also serve as a surface of said case.

With regard to the tilt adjustment mechanism, any may be utilized thatis equipped with a mechanism that moves the image detection device 20vertically integral with the holding member main body 71 by changing theamount of space between said main body 71 and bottom plate 72. Forexample, mechanisms that impart vertical motion via the rotation of ascrew by a motor, or via geared teeth may be utilized. In FIG. 4, tiltadjustment mechanisms A1˜A4 are provided in the four corners (fourlocations) in the space between holding member main body 71 and bottomplate 72. The heights of each tilt adjusting mechanism A1 through A4 areadjusted by a tilt data input portion (not shown) and a control portion(not shown) based on the detected tilt data.

FIG. 5 shows an example of a shift means 55. As shown in the figure, theshift means 55 is composed of: a shift mechanism Bx that moves holdingmember 70 which secures and holds image detection device 20 along mobileportion 56 which is capable of planar movement in the X-direction(left-right direction in the figure), and a shift mechanism By thatmoves said holding member 70 in the Y-direction (up-down direction inthe figure) The mobile portion, which is capable of planar movement inthe Y-direction, is not shown in the figure. The shift means 55 isstructured to move the image detection device 20 integrally with theholding member 70 vertically and horizontally within a plane. Withregard to the shift mechanisms Bx and By, any may be utilized that isequipped with a mechanism that moves holding member 70 in a planarfashion. For example, mechanisms that impart planar motion via screws orgeared teeth as for the aforementioned tilt adjustment mechanism, maybeutilized.

By the construction described above, imaging can always be performed ina state where the angle between the central axis L1 a of the radiationand the detection surface is maintained perpendicular, and an imagesuitable for use in diagnosis can be obtained.

Next, the third embodiment of the radiation imaging system of thepresent invention will be described. FIG. 6 and FIG. 7 are schematicviews that show the structure of the third embodiment of the radiationimaging system. The radiation imaging system of the third embodiment isa portable system of the type that automatically emits radiation L1 fromthe radiation source 10 at a point when the tilt of the radiation L1 tobe emitted therefrom in relation to the detection surface of theradiation image detection device 20 is substantially perpendicular, andwith regard to this point, it differs from the first and secondembodiments described above.

For this reason, the radiation imaging system of the third embodiment isequipped with a command means 60 that generates an exposure command tothe radiation source 10 at a point when the tilt of the radiation Li tobe emitted therefrom in relation to the detection surface of theradiation image detection device 20 is substantially perpendicular. Notethat this structure, in which the system is equipped with said commandmeans 60, can be combined with the system of either the first or secondembodiment.

The structure shown in FIG. 6 is an example of this, and it is thesystem of the second embodiment further provided with the command means60. The structure shown in FIG. 7 is one in which the tilt of theradiation image detection device 20 is changed manually (by an operator)and, as stated above, generates an exposure command at a point when thetilt of the radiation L1 in relation to the detection surface becomesperpendicular. It need not be said that in the case that the structureshown in FIG. 7 is adopted, there is no necessity to equip means toadjust the tilt of radiation source 10 or image detection device 20.Note however, that even in this case, a portable shift means 50 thatenables horizontal movement of the radiation source 10 may be provided.

In the case that the tilt on the radiation image detection device 20side is to be manually changed as in the structure of FIG. 7, to avoidirradiation of the operator by radiation, the operator should performsaid operation while wearing protective clothing, or the irradiationarea of radiation should be focused.

As to the command means 60, a structure is adopted which monitorsangular signal S or Sx and Sy output from the angular signal outputmeans, and generates an exposure command J to the radiation source 10when the tilt of the central axis L1 a of radiation L1 in relation tothe detection surface of the radiation image detection device 20 issubstantially perpendicular. As to the determination for when said tiltis perpendicular, in the case that radiation source 10 is oriented sothat its emission surface faces approximately straight downward, thatis, so that radiation L1 is emitted approximately straight downward, thepoint in time when the detection surface of the image detection deviceis approximately level can be made the point of perpendicularity.

By the construction described above, imaging can always be performed ina state where the angle between the central axis L1 a of the radiationand the detection surface is maintained perpendicular, and an imagesuitable for use in diagnosis can be obtained.

The preferred embodiments of the radiation imaging system and theradiation image detection device to be used with said system of thepresent invention have been described, but the present invention is notlimited to the embodiments described above.

For example, in each of the embodiments described above, electroniclevels integrally mounted on the radiation image detection device 20were utilized as the angular signal output means 30. However, aprojection sensor that utilizes light may be utilized as said means. Inessence, any mechanism that is capable of measuring the angle formed bythe central axis L1 a of radiation L1 and the detection surface of theimage detection device (incidence angle) maybe adopted as the angularsignal output means.

1. A portable radiation imaging system comprising: a radiation source;and a two dimensional radiation image detection device that records aradiation image by detecting the radiation emitted from said radiationsource and is transmitted through a subject; wherein both said elementsare structured to be carriable, further comprising an angular signaloutput means that outputs an angular signal which represents the degreeof tilt of the radiation emitted from said radiation source in relationto the detection surface of said radiation image detection device; and atilt adjustment means that adjusts said tilt of the radiation inrelation to the detection surface of the radiation image detectiondevice to become substantially perpendicular by changing the tilt angleof said radiation source based on said angular signal output from saidangular signal output means.
 2. A radiation imaging system according toclaim 1 further comprising a portable shift means that enableshorizontal movement of the radiation source.
 3. A radiation imagingsystem according to claim 2, wherein said shift means comprises screwsor geared teeth.
 4. A radiation imaging system according to claim 1further comprising a portable shift means that enables horizontalmovement of the radiation image detection device.
 5. A radiation imagingsystem according to claim 1, wherein said image detection devicecomprises a stimulable phosphor sheet.
 6. A radiation imaging systemaccording to claim 1, wherein said image detection device is located ata distance from a subject being imaged.
 7. A radiation imaging systemaccording to claim 1, wherein said tilt adjustment means comprisesscrews or geared teeth.
 8. A radiation imaging system according to claim1 comprising a scattered ray removal grid board adjacent to theradiation image detection device which prevents the occurrence of falseimages and enhances image reproducibility after radiation has beentransmitted through a subject.
 9. A radiation imaging system accordingto claim 1, wherein said angular signal output means is an electroniclevel or a projection style angle sensor.
 10. A radiation imaging systemaccording to claim 9, wherein said electronic level is integrallymounted on said two dimensional radiation image detection device.
 11. Aportable radiation imaging system according to claim 1, wherein saidangular signal output means is integral with said two dimensionalradiation image detection device.